1. Field of Disclosure
The present disclosure relates generally to the field of electronics and, more particularly, to devices and methods that dissipate heat from electronic components.
2. Discussion of Related Art
Modern electronic components produce excessive amounts of heat during operation. To ensure that the components do not overheat, system designers attach convective heat sinks to cool these components, by providing an efficient heat transfer path from the devices to the environment. A typical convective heat sink is designed to transfer heat energy from the high temperature component to lower temperature of the surrounding air. Such typical heat sinks attach to the components through a base and include fins or pins to increase the surface area of the heat sink within a given space.
FIG. 1 shows a well-known embodiment of a heat sink, which is generally indicated at 10. The heat sink 10 may be extruded from aluminum, having a base 12 and fins, each indicated at 14, that extend from a base 12. As shown in FIG. 1, the fins 14 extend perpendicularly from the base 12. By increasing the surface area of the heat sink 10, the heat transfer capacity of the heat sink increases. The surface area of the heat sink 10 may be increased by extending the fins 14 in one direction away from the electronic component, thus creating an extruded fin profile, or by providing more, smaller fins. The air heated by the component passes through the fins 14, thus transferring heat away from the heat sink 10 to the surrounding environment.
In a conventional extrusion process, aluminum is heated to a temperature just shy of its melting point and pressed through a die. With this process, there is a practical limit to how thin the fins of the heat sink can be relative to its length. There is also a practical limit to how far apart the fins can be spaced from one another relative to the length of the fins. For example, a heat sink produced by the conventional extrusion process can normally achieve a 10:1 ratio of the length of the fin in relation to the distance between adjacent fins.
In order to go beyond the length to distance limit, other techniques for fabricating heat sinks, such as bonded fin heat sinks and folded fin heat sinks, have been employed. However, both of these alternative approaches have drawbacks concerning limited thermal conduction in the assembly in between the base plate and the fins. Further, these known techniques have a considerable higher degree of labor cost and fabrication time cost than extruded heat sinks.
With the extrusion process, the cost of extruded heat sinks is proportional to the weight of the material used due to the fact that a primary cost driver in fabricating the extruded heat sink is the material cost. The most widely used material for heat sinks is aluminum. Extruded heat sinks are less expensive than bonded fin heat sinks and folded fin heat sinks (having equivalent masses) because of the lower labor and machine time costs for extruded heat sinks. However, folded fin heat sinks and bonded fin heat sinks may be formed more compactly with less mass since they can be made with longer, thinner and more closely spaced apart fins. Another drawback, in addition to cost, for the folded fin and the bonded heat sinks is that the connection between the base plate and the fins typically are made by some kind of glue, which has a lower thermal conductivity than solid aluminum.
In systems using forced cooling (for example, using a fan to move air through the heat sink), heat sinks with many thin fins are more efficient than heat sinks with fewer fat fins (having equivalent mass) since in the instance of forced cooling, air at high speed can be pressed between fins that are placed close together. In the instance where thin fins are placed close together, the heat sink has a very large surface compared to the volume. This makes the combination of forced cooling (using a fan) combined with thin fins that are closely space with one another extremely efficient.